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I'm just starting a project to build a universal Engineer's Remote Control Unit [EG. able to send the Panasonic 0xF2 code, etc.].

I have seen that IR LEDs come with (at least) three distinctly different coloured lenses, namely "Crystal Clear", "Blue" and "Black" ...Using Google, I can find no information about the difference made by the colour of the lens.

So my question is: Why do Infrared LEDs come with different coloured lenses?

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  • \$\begingroup\$ What do the datasheets tell you? In particular the colored lenses might point to some difference in spectral response. \$\endgroup\$ – Spehro Pefhany Jun 15 '15 at 12:13
  • \$\begingroup\$ The few datasheets I checked offered nothing immediately obvious. Same angle; same frequency (940nm)...The only thing I noticed was perhaps Blue indicated a GaAs element ...I also guessed that maybe the "Black" was to filter out unwanted light - but it is just a guess. \$\endgroup\$ – BlueChip Jun 15 '15 at 12:25
  • \$\begingroup\$ The different colours match the product cases just much better. \$\endgroup\$ – PlasmaHH Jun 15 '15 at 12:30
  • \$\begingroup\$ Since these are light emitters rather than detectors, I suspect the main reason for black (clear at IR wavelengths) is to prevent stray light from being refracted out the lens. The light blue may just be to indicate to assemblers that the LED is not a visible type. \$\endgroup\$ – Spehro Pefhany Jun 15 '15 at 12:32
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Depending of the lens material (and its color), the lens might act as an optical filter. It attenuates visible light but lets the infrared wavelengths pass through. To illustrate this, one could compare the spectral distribution figures between the datasheets of two similar IREDs (Infrared Emitting Diode), just with different lens colors.

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  • \$\begingroup\$ 1) I agree that it "might" be a filter (see above) 2) How would you know that the ONLY difference were the lens colour? 3) "IRED is... a term specifically applied to Excelitas IR emitters" [excelitas.com/Pages/Product/… \$\endgroup\$ – BlueChip Jun 16 '15 at 12:14
  • \$\begingroup\$ @BlueChip it seems that there is an error in the link. \$\endgroup\$ – Celal Ergün Dec 28 '17 at 7:01
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    \$\begingroup\$ @CelalErgün It seems the trailing ']' got appended to the URL ...try again: excelitas.com/Pages/Product/… \$\endgroup\$ – BlueChip Dec 29 '17 at 11:07

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